Allow materialized only (#563)

This change allows for just the materialized argument to be passed
and removes the sha256 values for haskell.nix's own materialized
nix files.

Author: hamishmack

lib/materialize.nix

@@ -1,12 +1,14 @@
 { pkgs, nix, runCommand, checkMaterialization }@defaults:
-{ sha256
-, sha256Arg      # Name of the sha256 argument for more meaningful
+{ sha256 ? null  # Has to make this a fixed output derivation
+, sha256Arg ? "sha256"
+                 # Name of the sha256 argument for more meaningful
                  # error messages when checking the materialization.
 , materialized   # null or path where to find materialized version of
                  # the output. If this is set but does not exist
                  # the derivation will fail but with a message
                  # advising how to populate it.
-, reasonNotSafe  # Some times there a reasont the derivation will
+, reasonNotSafe ? null
+                 # Some times there a reasont the derivation will
                  # not produce output that can be safely materialized.
                  # Set this to a string explaining why and materialization
                  # will not be used (if sha256 was set an error will be
@@ -37,7 +39,7 @@ let
         # Warn the user if they tried to pin stuff down when it is not safe
         traceIgnoringSha256 reasonNotSafe
           (traceIgnoringMaterialized reasonNotSafe calculateNoHash)
-    else if sha256 == null
+    else if sha256 == null && materialized == null
       then
         # Let the user know how to calculate a sha256 to use to make this
         # a fixed output derivation.
@@ -52,7 +54,7 @@ let
           calculateUseHash
     else
       # Everything is in place we can safely use the sha256 and materialized
-      calculateUseAll;
+      calculateUseMaterialized;
 
   # Build fully and check the hash and materialized versions
   checked = runCommand name {
@@ -119,17 +121,14 @@ let
       # Make sure output files can be removed from the sandbox
       chmod -R +w $out
     '';
-  calculateUseAll = 
-    # Skip right to expectedPath if it already exists
-    if materialized != null
-      then
-        assert __pathExists materialized;
-        runCommand name hashArgs ''
-          cp -r ${materialized} $out
-          # Make sure output files can be removed from the sandbox
-          chmod -R +w $out
-        ''
-      else calculateUseHash;
+  calculateUseMaterialized =
+    assert materialized != null;
+    assert __pathExists materialized;
+    runCommand name (pkgs.lib.optionalAttrs (sha256 == null) hashArgs) ''
+      cp -r ${materialized} $out
+      # Make sure output files can be removed from the sandbox
+      chmod -R +w $out
+    '';
 
   # Materialized location was specified, but the files are not there.
   missingMaterialized = materialized != null && !__pathExists materialized;

overlays/bootstrap.nix

@@ -386,7 +386,6 @@ in {
                 inherit (bootstrap.packages) cabal-install nix-tools hpack;
                 name = "alex"; version = "3.2.4";
                 index-state = self.haskell-nix.internalHackageIndexState;
-                plan-sha256 = "1adn8s46msqm2rl6yf01z2r81maa2001qh441j491gpmc3ki36n0";
                 materialized = ../materialized/alex;
             };
             alex = bootstrap.packages.alex-project.hsPkgs.alex.components.exes.alex;
@@ -396,7 +395,6 @@ in {
                 inherit (bootstrap.packages) cabal-install nix-tools hpack;
                 name = "happy"; version = "1.19.11";
                 index-state = self.haskell-nix.internalHackageIndexState;
-                plan-sha256 = "0swpwhlym4p3209qv90mfgq6zsaw99ipznm4pvd32mxzwq9s5q8i";
                 materialized = ../materialized/happy;
             };
             happy = bootstrap.packages.happy-project.hsPkgs.happy.components.exes.happy;
@@ -406,7 +404,6 @@ in {
                 inherit (bootstrap.packages) cabal-install nix-tools hpack;
                 name = "hscolour"; version = "1.24.4";
                 index-state = self.haskell-nix.internalHackageIndexState;
-                plan-sha256 = "0cnkczsh1xy7cc60q3blwa51qrjhf5mc89s34y9ab3x702a26b75";
                 materialized = ../materialized/hscolour;
             };
             hscolour = bootstrap.packages.hscolour-project.hsPkgs.hscolour.components.exes.HsColour;

overlays/ghc-packages.nix

@@ -59,15 +59,11 @@ let
         # (we need to upgrade `nix-tools` to Cabal 3 for them to work)
         skipBroken = self.lib.filterAttrs (pkgName: _:
           ghcName == "ghc865" || (pkgName != "base" && pkgName != "ghc-heap"));
-        sha256 = ghc-boot-packages-nix-sha256."${ghcName}" or null;
         materializedPath = ../materialized/ghc-boot-packages-nix + "/${ghcName}";
       in (self.haskell-nix.materialize ({
-          inherit sha256;
-          materialized = if sha256 != null && __pathExists materializedPath
+          materialized = if __pathExists materializedPath
             then materializedPath
             else null;
-          sha256Arg = "ghc-boot-packages-nix-sha256";
-          reasonNotSafe = null;
         }) (combineFiles "${ghcName}-boot-packages-nix" ".nix" (builtins.mapAttrs
           (_: sdistAndNix: sdistAndNix.nix) (skipBroken bootPackages))));
 
@@ -89,14 +85,6 @@ let
       iserv-proxy  = "utils/iserv-proxy";
     };
 
-  # Hashes needed to make ghc-boot-packages use fixed output derivations
-  # for the nix files.
-  ghc-boot-packages-nix-sha256 = {
-    ghc865 = "0n5bsi67mczbwch8a3dwf58hkignb8qswv7h707dqgc43himvq3b";
-    ghc882 = "1wpvy0f2m7l3h8fz0iag3q8zj6j4i7732x1f0lkxnr2whnv88dfb";
-    ghc883 = "147l5a7vm8dgyb2wz692p3n3fsvq8wbjn5wnjhabdgw4mxw0c2mm";
-  };
-
   # The nix produced by `cabalProject` differs slightly depending on
   # what the platforms are.  There are currently 3 possible outputs.
   ghc-extra-projects-type =
@@ -106,26 +94,6 @@ let
         then "cross"
         else "default";
 
-  # Hashes needed to make ghc-extra-projects use fixed output derivations
-  # for the nix files.
-  ghc-extra-projects-sha256 = {
-    default = {
-      ghc865 = "12mj0fmm0b0jys6pb2l7l9w2w5as5fiqkfav81mjlz9ic1rkqk92";
-      ghc882 = "0q4v1iryvd5xvnkb1s02a3v6x0lj73r8bsfxrs9bxipk22bcksm9";
-      ghc883 = "0dy6isqz41c0di5yf1mhyp0nbp6aw5m947b54l5074lkmc4f5alb";
-    };
-    windows = {
-      ghc865 = "1jizwsnmdr2iglispm9wmhhbdh2gh6yfvk8x1jbj0sk9pq21xwap";
-      ghc882 = "09ji5548bsqqa7iwphjxmc5i067ya6zh0v1hfls9acfrxax0sfgm";
-      ghc883 = "0gliadn1nj1i5y5hjz280h1kgzql97yfh4gy63k2g7xsldmzb57b";
-    };
-    cross = {
-      ghc865 = "10bckrm3qi1vymncjiv534b8nb8bgix8w8y91543xxwhzpmwml3f";
-      ghc882 = "0hamwh6x0vfki2c4kj132x2c2hqvr1r735cfd4yrygzf86drmyf0";
-      ghc883 = "0v8wq8i82c329kzi3yzv6ny63yaggbzdaaxbbklxwg16fawqn08p";
-    };
-  };
-
 # Given the ghc-extra-pkgs, we'll create a cabal.project
 # that contains all of them.  And then we call cabalProject
 # on it to generate the necessary cabal project exposing all
@@ -200,11 +168,8 @@ in rec {
       name = "ghc-extra-projects-${ghc-extra-projects-type}-${ghcName}";
       src = proj;
       index-state = self.haskell-nix.internalHackageIndexState;
-      plan-sha256 =
-        ghc-extra-projects-sha256."${ghc-extra-projects-type}"."${ghcName}"
-          or null;
       materialized =
-        if ghc-extra-projects-sha256."${ghc-extra-projects-type}" ? "${ghcName}"
+        if __pathExists materializedPath
           then materializedPath
           else null;
       ghc = self.buildPackages.haskell-nix.compiler.${ghcName};